What is the effect of desmopressin in DI management?

• A. Increases urine output
• B. Blocks ADH receptor
• C. Promotes aldosterone secretion
• D. Replaces ADH to reduce urine output and concentrate urine

Answer: (D)

In central diabetes insipidus, there isn’t enough antidiuretic hormone to signal the kidneys to conserve water. Desmopressin is a synthetic analog of ADH that mimics its action on the kidney’s collecting ducts. It binds to V2 receptors, increasing aquaporin-2 channels and promoting water reabsorption back into the bloodstream. This reduces urine output and makes the urine more concentrated, effectively treating the main problem in DI. It’s specifically used to replace ADH in central DI; it wouldn’t work the same in nephrogenic DI where the kidneys don’t respond to ADH. The other options would worsen DI or affect different systems (increasing urine output, blocking ADH, or altering aldosterone), which is why replacing ADH to reduce urine output and concentrate urine is the correct effect. Monitor for fluid balance and sodium levels to avoid hyponatremia or fluid overload.